1. Field of the Invention
The present invention relates to methods of encapsulating optical components and products produced by those methods.
2. History of the Prior Art
Optical components are exposed to a wide variety of detrimental environmental influences during use. Environmental influences may cause physical, chemical or optic damage to an optical component. For example, one kind of planar optical fiber coupler is comprised of optical fibers that .ire precision aligned and fastened via adhesive, typically light-curable acrylic, to a glass coupler substrate. The adhesive can absorb moisture from the atmosphere and change dimensions and rigidity, thereby lowering the precision alignment and increasing signal loss. Such environmental influences must be minimized to ensure optimal component life and performance.
Several means of protecting optical components have been proposed. One approach has been to place the optical component within a solid support or container. U.S. Pat. No. 5,091,989 is directed to a process for encapsulating a component for interconnecting optical fibers wherein a bar connected to the fibers is inserted and sealed with a sealing composition into an elongated housing with a U-shaped cross-section.
U.S. Pat. No. 4,707,069 is directed to a protective arrangement for an optical fiber coupler which arrangement includes a substantially cross-sectionally V-shaped support element which forms an open channel into which a portion of the optical fiber coupler is adhesively secured. Additional adhesive bodies connect a strip-shaped support element to the bare regions of the optical fiber just outside the coupling region. Most of the length of V-shaped support element is tightly surrounded by a shrunk tubular shielding, and open ends of the V-shaped support element are closed by respective seals. Jacketed regions of the coupler are surrounded by shrunk tubular bend limiters which pass through the respective seals. This assembly is embedded in a receiving channel of a housing member with encapsulating material.
U.S. Pat. No. 4,714,316 is directed to an optical fiber unit having a protective assembly. The protective assembly includes a preformed internal protective body, an outer protective body surrounding the internal protective body, a mass of relatively soft uniting material disposed in a manner to secure the internal protective body to a preformed portion of the outer protective body, and stress relief means associated with the outer protective body enabling the fibers to extend from the internal protective body through the outer protective body so as to prevent breakage of the fibers under conditions of stress.
The above arrangements, while providing physical strength, are still susceptible to moisture and chemicals. A different approach was taken in Japanese patent application 60-107007 (the '007 application), which is directed to a manufacturing method for a fused optical fiber coupler. The method disclosed includes: removing the metal coating layer of pieces of metal-coated optical fibers; mutually fusing-adhering together the exposed portions of the optical fibers; and, immediately after fusing the exposed fibers, forming a metal reinforcing layer on the coupled portion of the optical fibers under an anhydrous atmosphere.
The metal reinforcing layer is formed in two steps. A primary metal layer is formed on the exposed portion of the fibers in a reaction container which has been evacuated and which has then had an inert gas, such as argon free from water, introduced to create an anhydrous atmosphere. The primary layer of metal is applied within the reaction container by sputtering or vacuum vapor deposition. A secondary layer of metal is then applied over the primary layer for mechanical strength. This secondary metal layer is formed by pouring molten metal around the primary metal layer or by plating.
The method of the '007 application is cumbersome to perform since much of it must be carried out in an anhydrous atmosphere and since it requires sputtering or vapor deposition equipment. The '007 application teaches that the molten metal may not be applied directly to the organic material of the coupler. The molten metal may only be applied over the primary metal layer which has been applied by sputtering or vacuum vapor deposition. Furthermore, the above method is only taught for fused optical fiber couplers, not other couplers or optical components.
Therefore, a need exists for a method of protecting optical components that minimizes moisture adsorption and chemical degradation, provides structural protection and which is relatively cheap, fast and easy to perform.